LONDON - Twelve people have been confirmed dead in a huge fire at a London tower block and the death toll is expected to rise, police said on Wednesday.

Fire engulfed the 24-storey block of flats in central London in the early hours of Wednesday. More than 50 people were injured and some residents were trapped inside the towering inferno.

Massive flames licked up the sides of the block as 200 firefighters battled the blaze for hours along with 40 fire engines. Flumes of black and grey smoke were billowing high into the air over London hours after the blaze was sparked.

London Fire Brigade reported fatalities and said the fire had engulfed all floors from the second to the top of the Grenfell Tower, where several hundred people lived on the Lancaster West Estate in west London.

"At this time I am very sad to confirm that there have been a number of fatalities, I cannot confirm the number at this time due to the size and complexity of this building," Dany Cotton, Commissioner of the London Fire Brigade told reporters.

London Ambulance Service said that 50 patients had been taken to five hospitals following the fire.

London Mayor Sadiq Khan demanded answers following the deadly blaze. "These questions are really important questions that need to be answered," Khan told BBC Radio.

"Across London we have many, many tower blocks and what we can't have is a situation where people's safety is put at risk because of bad advice being given or if it is the case, as has been alleged, of tower blocks not being properly serviced or maintained."

Some people were trapped in the fire, with residents desperately shouting for help from windows on upper floors as the fire spread, some British media reported.

"This is a large and very serious incident and we have deployed numerous resources and specialist appliances."

More than 20 ambulance crews were at the scene. London Mayor Sadiq Khan said a "major incident" had been declared. Police closed the A40, a major road leading out of west London, while some parts London's underground train network were closed as a precaution.

The cause of the fire, which broke out just before 1 a.m. (0000 GMT), is not known, the Fire Brigade said. Residents said repairs, including the addition of some sort of cladding, had been made to the exterior of the block recently.